The KEYS subsystem in the Linux kernel before 3.18 allows local users to gain privileges or cause a denial of service (NULL pointer dereference and system crash) via vectors involving a NULL value for a certain match field, related to the keyring_search_iterator function in keyring.c. It was discovered that a NULL pointer dereference existed in the keyring subsystem of the Linux kernel. A local attacker could use this to cause a denial of service (system crash).